The present invention relates to an in-line roller skate wheel and a method and apparatus for its manufacture. More specifically, the present invention relates to a wheel having a urethane hub and solid urethane tire of a unique shape and the mold configuration required to cast the tire.
In-line roller skates have been in existence since the 18th century, the first recorded having been constructed by a Dutchman who wanted to practice ice skating during warm weather by mounting wooden spools under his boots and skating on dry land. Other generally unsuccessful attempts at in-line roller skates followed but then, in the 19th century, the four-wheel skate with two pairs of wheels in a rectangular configuration was developed and took over the skating world. In-line skates were used very sparingly, mostly by ice skaters for warm-weather cross-training. In the early 1980""s, a pair of in-line skates was created and the concept greatly improved upon by a pair of ice hockey players who mounted polyurethane wheels under ice skating boots and, due to the vastly improved performance provided by these skates, the sport of in-line skating mushroomed. Along with increased popularity came the demand for even more improvements in performance and durability.
Today""s in-line skaters include racers, roller hockey players, serious ice hockey players looking for a cross-training device, stunt skaters, and casual users who only desire exercise and a smooth ride. Manufacturers have developed wheels of various profiles and hardness values to enhance sliding, gripping, maneuverability, speed, comfort and durability depending on the user""s desire and skill level. Large diameter wheels with minimal tire flexing to reduce rolling resistance are generally used when speed is desired. Smaller diameter wheels with shock absorbing properties are preferred for most recreational skating while those doing stunts such as rail slides require wheels of an even smaller diameter and high hardness value. Two popular types of wheels have emerged over the past two decades to meet these diverse needs, those containing pneumatic tires made by casting polyurethane around an annular bladder, and those with solid tires made by casting or injection molding polyurethane in the desired shape around a hard polyurethane or nylon hub.
Pneumatic tire designs have been proposed of a construction similar to automobile tires with a pneumatic bladder encapsulated in polyurethane. These wheels provide a cushioned ride and, containing less polyurethane, are generally lighter than a solid wheel. They provide good grip and shock absorbing properties and are very suited to use on uneven surfaces and when encountering rocks and other road hazards. Although these wheels are well suited to these applications, they are generally more complex and expensive than solid tire wheels. U.S. Pat. Nos. 5,641,365, 6,085,815 and 6,102,091 to Peterson et al assigned to the assignee of the instant application and U.S. Pat. No. 5,853,225 to Huang disclose wheels of this type.
Solid tires are generally constructed of solid polyurethane tire bodies molded about a hub. Diameter, profile and hardness are adjusted for the skater""s needs. U.S. Pat. No. 5,312,844 to Gonsior et al discloses a wheel with a thermoplastic polyether type polyurethane which is injection molded unto the hub to form a tire which is the width of the tire support ring at the ring contact radius and curves axially inwardly and radially outward to the tread surface. This shape tire is lacking in flexibility and ability to grip the ground during fast maneuvers. U.S. Pat. No. 5,567,019 to Raza et al discloses a similar wheel also with an injection molded tire of thermoplastic polyether type polyurethane and similar shape. Again, this shape tire is lacking in flexibility and ability to grip the ground during fast maneuvers. The manufacturing process is also relatively expensive.
U.S. Pat. No. 5,573,309 to Bekessy describes a wheel with a tapered tire deflection controlling rim extending circumferentially about the tire receiving shoulder, with rim side walls extending radially outward from a wide base at the tire receiving shoulder to a narrow peripheral surface. A resilient tire engages the tire receiving shoulder and encases the tapered tire deflection controlling rim. The tire includes an annular high friction shoulder situated radially inward and axially outward of its ground engaging outer surface. Deflection of this tire is said to allow use of more sidewall tire material for better compression and, in cooperation with the annular shoulder on the tire, cause progressively more tire material to contact the support surface as the skater turns, the harder the turn, the more surface contact for maintaining control. One configuration of this tire has recessed braking dimples situated about its ground engaging surface and radially inward of the tread section. The recessed braking dimples create channels of non-contact intended to reduce frictional resistance to a sideways skid when the skater is coming to a stop by tipping the skates to a maximum angle and skidding sideways to a stop. Although providing a good compromise between speed and gripping ability, the profile of this wheel is not optimized for weight reduction.
U.S. Pat. No. 5,655,784 to Lee discloses a solid tire mounted on a light weight fiber-reinforced hub to reduce flex and attain greater speed. U.S. Pat. No. 5,725,284 to Boyer discloses a wheel constructed of a plurality of layers of material disposed concentrically about a hub with the hardest material being on the outermost layer. U.S. Pat. No. 5,829,757 to Chiang et al discloses an in-line skate wheel with materials of similar hardness but different coefficient-of-friction values on different portions of the tires surface. The braking portion of the tire contains a high coefficient-of-friction material while the normal skating surface includes a high proportion of the low coefficient-of-friction material. This is touted as allowing the skater to proportionally engage the braking surface and control braking by leaning into the wheel and changing the angle to increase braking action.
These wheels each provide specific benefits but are generally complex, difficult to manufacture, and not optimized for high speed competition such as roller hockey and racing. There exists the need for a lightweight skate wheel which will provide a fast, smooth ride with excellent maneuverability and durability but without the complexity and expense of producing multi-segmented or pneumatic tires. There is also need to provide a method and apparatus for casting a wheel using a simple one piece tire, cast from urethane, and allowing use of unique profiles to reduce weight and enhance performance for any desired skating conditions.
The present invention includes many aspects. In one aspect it is in the form of a sculptured lightweight narrow in-line skate wheel particularly suited for, but not limited to, roller hockey and racing. The wheel includes a relatively hard, lightweight urethane hub and a solid urethane tire body with reduced hardness relative to the hub. The hub is constructed with a narrow axial support flange to cause the body of the wheel to be formed at its radially inner extent with a correspondingly narrower tire body width tapered axially inwardly from the opposite sides to cooperate in providing a low moment of inertia. In one embodiment the tire body is configured with a narrow crown to cooperate with the low moment of inertia to facilitate shifting of the wheel quickly from a turning position inclined in one direction to a position inclined in the opposite direction.
In one embodiment, the lightweight hub is formed with a transverse, annular bearing housing with oppositely opening bearing glands for insertion of a pair of bearings to mount on a skate wheel axle. The hub projects radially outward from this bearing housing in the form of an annular support disk which carries the annular support flange. The tire is mounted on the annular support flanges and encases a stabilizer ring that projects radially outwardly from the support flange. The radial stabilizer ring projects radially outwardly to cooperate in forming a tall profile projecting radially outwardly into the tire body to provide support under the tread to decrease deflection and rolling resistance, thus providing greater straight-line speed. The radial stabilizer ring profile is relatively thin, allowing a greater amount of the softer tire material on the sidewalls, promoting increased grip and maneuverability.
In one embodiment the hub is sectioned into two axial flanking sections which join to form the hub itself. The annular support disk may be formed with an annular tube or shell configured with the lightening cavity. Such shell and/or hubs may be sectioned to provide for ease of fabrication in sections to be joined by a mechanical joint and/or adhesive.
In one aspect of the present invention, a urethane wheel is formed by a hub fitting is constructed of first and second annular sections forming a bearing housing and an annular lightening shell concentric about the housing, with the shell being formed of confronting half tube walls terminating in concentric confronting edges, the edges including interfitting tongue and grove joint, constructed to snap together.
The present invention contemplates a cost effective method for manufacturing the wheel. The method employs a mold having annular upper and lower mold sections and a back pin section. The lower mold section is formed with an annular mold cavity section defining a central annular lower hub cavity for receiving a hub formed with the annular support flanges of a predetermined axial width and an outer lower tire body cavity section. The upper mold section is constructed to mate with the lower mold section and cooperates therewith to form a tire body cavity section curving radially inwardly and axially outwardly from a tread crown to form a maximum tire body width greater than the predetermined axial width of such support flanges, the top cavity wall projecting radially inwardly and axially outwardly to terminate in an annular sprue wall. The tire body cavity section is constructed so the lower annular support flange of the hub sealingly engages the wall of such cavity section and the back pin is constructed with an annular sealing lip to form a seal against the upper annular support flange on such hub. The pin further forms a portion of the tire""s profile, curving upwardly from the annular support flange to terminate in a back pin sprue wall spaced radially inwardly from and concentric with the upper mold section sprue wall to form an annular sprue inlet for receipt of prepolymers, curatives and pigment additives.
To form a wheel, a preformed hub is placed in the lower mold section, the upper mold section is then positioned on the lower mold section, and the back pin is engaged with the hub. Prepolymers, curatives and pigment additives which will interact to form a polyurethane are then introduced through the sprue inlet to fill the tire body cavity and surround and bond to the annular support flanges and tire support rim portions of the hub to cooperate in forming a wheel. The wheel is then removed from the mold and trimmed.
As will be apparent to those skilled in the art for the sectioned hubs the separate sections therein may be fabricated separately and joined together to complete the finished hubs for receipt of the urethane tire material to be molded therein.
Other features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features of the invention.